Personally, would ONLY shoot the 10ga nitros 2.5 and 3 oz loads out of a ithaca mag10/sp10 , or a browning 10, ...only .....
Since it sounds like your gun has fixed gull chokes , your best option is the federal #7 hw with the flight control wad , you might get lucky at get a 150+ pattern with a fixed choke , a box of 5 will set you back 30$ at bass pro, CLEAN YOUR BARREL THOUGHLY BETWEEN SHOTS , the plastic fowling buildup realy affects pattern performance
If both barrels shoot true poi/poa , one can shoot tight and the other more open, and you have selective triggers ...you have yourself a awsome turkey gun that can take close and longer shots at desire , then get a 5$ roll of camo gun tape and go turkey hunting
